In a manufacturing process of a semiconductor device, a cleaning treatment of supplying a cleaning chemical liquid to a surface of a semiconductor wafer to remove an unwanted matter from a surface of its substrate.
A single-substrate-processing apparatus processing semiconductor wafers one by one comprises a spin chuck rotating a substrate while holding the substrate horizontally, and a nozzle supplying a cleaning chemical liquid to a surface of the substrate held by the spin chuck. The cleaning chemical liquid is supplied to the surface of the substrate while the spin chuck which holds the substrate is being rotated. Thus, the cleaning chemical liquid reaches an entire area of the surface of the substrate to remove an unwanted matter from the entire area of the surface of the substrate.